This invention relates to apparatus for securing wrappers around generally cylindrical objects, for example around stacks of disc-like tablets.
Apparatus is known in the prior art which will receive a train of wrappers and a train of generally cylindrical objects such as a stack of disc-like tablets, and which will secure the wrappers to and around the exterior cylindrical surface of the objects. More specifically, it is known in the prior art to advance each of the successive cylindrical objects and each of the corresponding wrappers into a wrapping machine which wraps the wrapper entirely around the exterior of the object and secures it in place. To accomplish this, a gluing wheel has been used to lay down a layer of glue on the underside of the wrapper just prior to wrapping, so that when the wrapper is wrapped around the object and overlapped somewhat upon itself, it is glued in the desired position.
It has also been proposed to use as the wrapper a paper-like material coated on one surface with a layer of a heat-activatable adhesive, and instead of applying glue to the wrapper, applying a blast of hot air directly to the heat-activatable layer just prior to the wrapping operation, whereby upon completion of the wrapping the wrapper is again secured around the object.
The latter type of system is disclosed in U.S. Pat. No. 2,952,376, issued Sept. 13, 1960 to Daniel L. Orloff, which discloses the application of labels to round bottles by using a label having a thermally-activatable layer on one surface thereof and applying a blast of hot air to a portion of the heat-activatable surface just prior to application of the label to the bottle. The times and durations of the air blasts may be controlled by a solenoid valve, and the blast is released through a series of holes in a tube overlying the position assumed by the label just prior to wrapping; heating elements are housed in the air-blast supplying tube.
While this type of arrangement may be suitable for some purposes, it has been found to be inapplicable to certain classes of wrapper-applying machines. For example, in one known commercial type of machine with respect to which the present invention will be described in detail, it has been deemed not practical to apply a blast of hot activating air to the exposed heat-activatable heated layer, because of space and other practical considerations.
It is therefore an object of the present invention to provide a new and useful method and apparatus for the application of an encircling band of flexible sheet material (herein referred to as a wrapper) to the exterior of a generally cylindrical object.
Another object is to provide such method and apparatus which are capable of functioning reliably at a high rate of speed in a commercial production environment.
It is also an object to provide such method and apparatus which do not require that the hot air blast be applied directly to the heat-activatable layer on the sheet or label, and which therefore can be utilized in situations where such application would be inconvenient or impossible.
A still further object of the invention is to provide a new, especially compact apparatus for providing an air blast of very high temperature and very short duration, suitable for use in the above-identified method and apparatus.